Light-emitting device using a group III nitride compound semiconductor and a method of manufacture

ABSTRACT

A process of forming separation grooves for separating a semiconductor wafer into individual light-emitting devices, a process for thinning the substrate, process for adhering the wafer to the adhesive sheet to expose a substrate surface on the reverse or backside of the wafer, a scribing process for forming split lines in the substrate for dividing the wafer into light-emitting devices, and a process of forming a mirror structure comprising a light transmission layer, a reflective layer, and a corrosion-resistant layer, which are laminated in sequence using sputtering or deposition processes. Because the light transmission layer is laminated on the adhesive sheet, gases normally volatilized from the adhesion materials are sealed and do not chemically combine with the metal being deposited as the reflective layer. As a result, reflectivity of the reflective layer can be maintained.

[0001] This is a patent application based on a Japanese patentapplication No. 2000-96495 which had been filed on Mar. 31, 2000.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a light-emitting device using agroup III nitride compound semiconductor and a method for manufacturingsuch a device. In particular, the present invention relates to thestructure of a mirror structure formed on the reverse side of asubstrate and a method for forming the mirror structure.

[0004] 2. Description of the Related Art

[0005] A variety of light-emitting devices using group III nitridecompound semiconductor comprising a mirror structure formed on thereverse side or backside of a substrate and a variety of methods formanufacturing such devices are generally known in the art. For example,Japanese patent Application Laid-Open (kokai) No. 11-126924 (Title:“Method of manufacturing gallium nitride compound semiconductorelement”) (hereinafter referred to as Reference 1), Japanese PatentApplication Laid-Open No. 11-126925 (hereinafter referred to asReference 2), Japanese Patent Application Laid-Open No. 5-129658(hereinafter referred to as Reference 3), and Japanese PatentApplication Laid-Open No. 11-261112 (hereinafter referred to asReference 4) disclose other such LEDs.

[0006]FIG. 14 shows a cross-sectional view of a conventionallight-emitting semiconductor device 900 using a group III nitridecompound semiconductor of the type disclosed in the aforementionedReference 1.

[0007] A sapphire substrate 11 is formed into an approximately squareshape. A buffer layer 12 and an n-type contact layer 13 (hereinafteralternatively referred to as “a high carrier concentration n⁺-layer 13”or “an n⁺-layer 13”) are then sequentially formed on the substrate 11.An n-type clad layer 14 is then formed on the high carrier concentrationn⁺-layer 13.

[0008] An emission layer 15 having a multiple quantum well (MQW)structure comprising a plurality of alternating barrier layers 151 andwell layers 152 is then formed on the n-type clad layer 14. A p-typeclad layer 16 is then formed on the emission layer 15 and a p-typecontact layer 17 is formed on the p-type clad layer 16.

[0009] A positive electrode 18A which transmits light is formed on thep-type contact layer 17. The positive electrode 18A comprises a firstthin-film metal layer which is adjacent to the contact layer 17 and asecond thin-film metal layer which is adjacent to the first thin-filmmetal layer. A negative electrode 18B, which is formed on the n⁺-layer13, comprises a plurality of metal film each film having a multiplelayer structure. A metal electrode pad 20 is then formed on a portion ofthe positive electrode 18A.

[0010] On the reverse side of the substrate 11 (sapphire substrate 11),a metal layer 90 (mirror structure 90) consisting of about 200 nm ofaluminum (Al) is then formed.

[0011] Generally, a sapphire substrate is hard. In order to divide asemiconductor wafer precisely, therefore, separation grooves or splitlines (also referred to as scribe lines) are formed on both thesemiconductor side and the reverse side of the substrate after formingthe electrodes.

[0012] When split lines are formed on the electrode side (upper side) ofthe semiconductor wafer, the substrate is still required to maintain acertain mechanical strength. A certain thickness of the substrate ispreferred, typically about several hundred microns (μm). Then, in orderto separate the individual light-emitting semiconductor devicesproperly, the substrate is polished to further reduce its thickness. Thesplit lines are then scribed on the reverse side, or the polishedsurface, of the substrate.

[0013] In the conventional manufacturing processes, however, leave twosignificant problems unsolved. As a result, the mass production, sale,and use of such light-emitting devices using group III nitride compoundsemiconductor and including a reflective metal layer has not been easy.

[0014] The first problem relates to the formation of the split lines.

[0015] Before forming the metal layer on the reverse side of thesubstrate, it is necessary to form split lines (scribe lines) on thereverse side of the semiconductor wafer or substrate.

[0016] This is because scribing cutters are typically formed from smallgrains of diamond shaped into a blade. Because the blade of such ascribing cutter will tend to be clogged by any metal layer laminated onthe reverse side of the substrate, the split lines cannot be formedafter the metal layer is formed.

[0017] Further, the scribing cutter must be positioned precisely to cutonly the predetermined regions. However, a metal layer formed on thesurface to be cut would hinder the positioning. To solve this problem,the conventional method, i.e., not forming the metal layer onpredetermined regions of the reverse side of the substrate used forpositioning, as disclosed in the above-mentioned references, may beused. By using such a conventional method, however, semiconductorlight-emitting devices are formed without the necessary metal layer toform the mirror structure. Because these devices cannot becommercialized, a portion of the wafer is wasted and productionefficiency is reduced.

[0018] Yet another problem associated with the conventional scribingprocess is that a semiconductor wafer being scribed is typically fixedto an adhesive sheet. When the metal layer is being formed on thereverse side of the substrate, a portion of the sheet materials, inparticular the adhesive, tends to volatilize and release abundant andundesirable gases during the deposition of the metal layer. Becausethese gases interact chemically with the deposited or sputtered metals,the reflectivity and affinity (adhesion) of the resulting metal layer tothe substrate can be significantly lowered.

[0019] Another significant problem relates to the corrosion resistanceof the resulting mirror structure.

[0020] When adhesives (such as paste materials including silver are usedto bond the mirror structure of the light-emitting device to otherstructures such as leadframes, submounts, and stem contacts, theresulting alloying and oxidation effects can cause the metal layer todeteriorate and, as a result, lower the reflectivity of the mirrorstructure.

[0021] The reflective layer of the light-emitting device may also bedamaged during and/or after the scribing and separation processes. Whenthe reflection layer is too severely damaged, quantity of reflectedlight will decrease and the reflective layer may be partially orcompletely peeled off (delamination).

SUMMARY OF THE INVENTION

[0022] The present invention overcomes each of the aforementionedproblems as well as other problems. Thus, an object of the presentinvention is to provide a structure for and a method of constructing alight-emitting device which has an increased luminous output and alonger performance life that can be mass-produced at comparatively lowcost.

[0023] In order to solve the above-noted problems, a first object of thepresent invention is to provide a light-emitting semiconductor devicecomprising plural semiconductor layers comprising group III nitridecompound semiconductors that are laminated onto a substrate by crystalgrowth, and an improved mirror structure. The mirror structure is formedby laminating a light transmission layer and a reflective layer on thereverse side of the substrate, i.e., the side of the substrate oppositethe emission layer. The light transmission layer may be formed from avariety of metal oxides and ceramic materials having sufficient luminoustransparency. The reflective layer preferably consists of one or moremetals and reflects light emitted from the emission layer.

[0024] A second object of the present invention is to provide alight-emitting semiconductor device comprising plural semiconductorlayers, comprising group III nitride compound semiconductors that arelaminated onto a substrate by crystal growth, and a mirror structure.The mirror structure is formed by laminating a reflective layer, whichcomprises metals and reflects light emitted from the emission layer, anda corrosion-resistant layer, which comprises at least a metal oxide or aceramic material.

[0025] A third object of the present invention is to laminate acorrosion-resistant layer comprising a metal oxide or a ceramic materialhaving luminous transparency over the operative layers, including thelight transmission layer and the reflective layer that forms the mirrorstructure.

[0026] A fourth object of the present invention is to form thereflective layer by using at least one metal selected from aluminum(Al), silver (Ag), or one of their alloys.

[0027] A fifth object of the present invention is that a thickness ofthe reflective layer is within a range of between 5 nm and 20 μm.

[0028] A sixth object of the present invention is to form the lighttransmission layer by using metal oxides and oxides having luminoustransparency, such as Al₂O₃, TiO₂, MgO, MgCO₃, Ta₂O₅, ZnO, In₂O₃, SiO₂,SnO₂, and ZrO₂.

[0029] A seventh object of the present invention is to provide a lighttransmission layer having a thickness within a range of between 5 nm and10 μm.

[0030] An eighth object of the present invention is to form thecorrosion-resisting layer by using at least one metal oxide or oxide,such as Al₂O₃, TiO₂, MgO, MgCO₃, Ta₂O₅, ZnO, In₂O₃, SiO₂, SnO₂, or ZrO₂,a metal carbide, a metal nitride, or a metal boride that is corrosionresistant.

[0031] A ninth object of the present invention is to provide acorrosion-resisting layer having a thickness that is within a range ofbetween 5 nm and 10 μm.

[0032] A tenth object of the present invention is to provide a substratethat comprises sapphire and has a thickness within a range of between 75μm and 150 μm.

[0033] An eleventh object of the present invention is to form thereflection layer by using at least one metal such as rhodium (Rh),ruthenium (Ru), platinum (Pt), gold (Au), copper (Cu), palladium (Pd),chromium (Cr), nickel (Ni), cobalt (Co), titanium (Ti), indium (In),molybdenum (Mo), or an alloy of at least one of these metals.

[0034] A twelfth object of the present invention is to provide areflective layer that has a multiple layer structure comprising pluralmetal layers.

[0035] A thirteenth object of the present invention is to provide amethod for manufacturing the light-emitting device using a group IIInitride compound semiconductor described above that further comprises aprocess of forming a mirror structure including the steps ofsequentially laminating a light transmission layer, and/or a reflectivelayer, and/or a corrosion-resistant layer on the reverse side ofsubstrate, i.e., the side opposite the plural semiconductor layers.

[0036] A fourteenth object of the present invention is to provide amethod for manufacturing the light-emitting device further comprising aprocess for breaking the semiconductor wafer into individuallight-emitting semiconductor devices.

[0037] A fifteenth object of the present invention is to provide amethod for manufacturing the light-emitting device further comprisingthe following sequence of steps a process for forming separation groovesto separate the semiconductor wafer into individual of light-emittingsemiconductor devices by cutting the electrode side of the wafer to apredetermined depth; a lamellar process for grinding or polishing thesubstrate to a predetermined thickness; an adhesion process for adheringthe semiconductor wafer to an adhesive sheet so that the reverse side ofthe semiconductor wafer is exposed for processing; a scribing processfor scribing the split lines on the reverse side of the semiconductorwafer to divide the wafer into individual light-emitting semiconductordevices; and the process for forming the mirror structure.

[0038] Accordingly, above described problems can be solved by utilizingof these processes.

BRIEF DESCRIPTION OF THE DRAWING

[0039]FIG. 1 is a cross-sectional view of a light-emitting device 100using a group III nitride compound semiconductor of the presentinvention;

[0040]FIG. 2 is a cross-sectional view showing a process of formingseparation grooves in a semiconductor wafer 200 in accordance with firstand second embodiment of the present invention;

[0041]FIG. 3 is a cross-sectional view showing a lamellar process of thesemiconductor wafer 200 in accordance with first and second embodimentof the present invention;

[0042]FIG. 4 is a plan view showing the semiconductor wafer 200 or 300from a substrate (11 b) side after the lamellar process in accordancewith first and second aspects of the present invention;

[0043]FIG. 5 is a cross-sectional view of a semiconductor wafer 201showing an adhering process in accordance with the first embodiment ofthe present invention;

[0044]FIG. 6A and 6B are plan views showing the adhering process and ascribing process in accordance with the first embodiment of the presentinvention;

[0045]FIG. 7 is a cross-sectional view of the semiconductor wafer 201showing the scribing process in accordance with the first embodiment ofthe present invention;

[0046]FIG. 8 is a cross-sectional view of the semiconductor wafer 201showing a process of forming a mirror structure in accordance with thefirst embodiment of the present invention;

[0047]FIG. 9 is a table showing characteristics of a light-emittingdevice 100 using a group III nitride compound semiconductor which wasseparated from a semiconductor wafer corresponding to water 201 in FIG.5 by a breaking process in accordance with the first embodiment of thepresent invention;

[0048]FIGS. 10A and 10B are plan views of a semiconductor wafer 300showing processes of forming mask and the mirror structure in accordancewith the second embodiment of the present invention;

[0049]FIG. 10C is a cross-sectional view of the semiconductor wafer 300showing processes of forming the mask and the mirror structure inaccordance with the second embodiment of the present invention;

[0050]FIG. 11 is a cross-sectional view of the semiconductor wafer 300showing the process of forming the mirror structure in accordance withthe second embodiment of the present invention;

[0051]FIG. 12 is a cross-sectional view of a semiconductor wafer 301showing an adhering process in accordance with the second embodiment ofthe present invention;

[0052]FIG. 13 is a cross-sectional view of the semiconductor wafer 301showing a scribing process in accordance with the second aspect of thepresent invention; and

[0053]FIG. 14 is a cross-sectional view of a conventional light-emittingdevice 900 using a group III nitride compound semiconductor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0054] The present invention will now be described by way of specificembodiments.

[0055] In the present invention, by forming the light transmission layerwhich comprises at least one metal oxide or ceramic having sufficientluminous transparency between the substrate and the reflective layer,gases volatilized from the adhesive sheet can be controlled. As aresult, the reflectivity of the reflective layer can be maintained at ahigh level.

[0056] By forming a corrosion-resistant layer comprising at least onemetal oxide or ceramic material having luminous transparency on the topof the layers formed in the mirror structure, the problem of corrosionresistance of the mirror structure can be solved. That is because thecorrosion-resistant layer can protect the reflective layer. Thecorrosion-resistant layer is preferably formed by using a material whichis not easily alloyed with the reflection layer and has mechanicalstrength, hardness, and corrosion resistance. More preferably, thematerial can be easily and firmly bonded to materials such as leadframe,submount, or stem using solder. Considering these conditions, thecorrosion-resistant layer preferably comprises a material such as atleast one metal oxide or ceramic material.

[0057] By forming the reflective layer using at least one metal selectedfrom aluminum (Al), silver (Ag), and their alloys, the reflectivity ofthe reflective layer is extremely high.

[0058] The thickness of the reflective layer is preferably in a rangebetween 5 nm and 20 μm. Although it may depend on the kinds of metalsconstituting the layer, the thickness of the reflective layer is morepreferably in a range between 30 nm and 1000 nm, and most preferably ina range between 50 nm and 500 nm. When the reflective layer is too thin,its reflectivity is reduced. When the reflective layer is too thick, toomuch metal material, processing time and other resources, are requiredto form the layer, thereby unnecessarily increasing the cost of formingthe reflective layer.

[0059] The light transmission layer is formed by using at least oneoxide having luminous transparency such as Al₂O₃, TiO₂, MgO, MgCO₃,Ta₂O₅, ZnO, In₂O₃, SiO₂, SnO₂, and ZrO₂.

[0060] The thickness of the light transmission layer is preferably in arange of 5 nm to 10 μm. Although it may depend on the kinds of materialsused to form the layer, the thickness of the light transmission layer ismore preferably in a range between 10 nm and 500 nm, and most preferablyin a range between 20 nm and 300 nm. When the light transmission layeris too thin, its ability to adhere to the substrate is reduced. When thelayer is too thick, its luminous transparency decreases accordingly andtoo much material processing time and other resources are required toform the layer, thereby unnecessarily increasing the cost of forming andreducing the performance of the light transmission layer.

[0061] The corrosion-resistant layer is formed by using at least onematerial having corrosion resistivity such as an oxide selected fromAl₂O₃, TiO₂, MgO, MgCO₃, Ta₂O₅, ZnO, In₂O₃, SiO₂, SnO₂, and ZrO₂, or ametal carbide, a metal nitride, or a metal boride.

[0062] The thickness of the corrosion-resistant layer is preferably inrange between 5 nm and 10 μm. Although it may depend on the materialsused to form the layer, the thickness of the corrosion-resistant layeris more preferably in a range between 30 nm and 500 nm, and mostpreferably in a range between 50 nm and 300 nm. When thecorrosion-resistant layer is too thin, the corrosion resistance of themirror structure is reduced. When the layer is too thick, too muchmaterial, processing time and other resources are required to form thelayer, thereby unnecessarily increasing the cost of forming thecorrosion-resistant layer.

[0063] By forming the substrate comprising sapphire to a thickness in arange between 75 μm and 150 μm, the individual semiconductor devices canbe divided without forming unnecessary non-functional devices resultingfrom the scribing process used to draw split lines (scribe lines) andother scribe processes. The thickness of the substrate is morepreferably in a range between 80 μm and 100 μm, and most preferably in arange between 85 μm and 100 μm.

[0064] When the substrate is too thick, scribing processes cannot becarried out without forming non-functional devices. When the substrateis too thin, the substrate is too weak to endure the necessary washingand scribing processes.

[0065] By forming the reflective layer using at least one metal selectedfrom rhodium (Rh), ruthenium (Ru), platinum (Pt), gold (Au), palladium(Pd), chromium (Cr), nickel (Ni), cobalt (Co), titanium (Ti), indium(In), molybdenum (Mo), and their alloys, the device can effectivelyprovide the effect described above.

[0066] Rhodium (Rh) has a relatively high reflectivity, althoughsomewhat lower than silver (Ag) and aluminum (Al), and is useful forforming the reflective layer. In particular, because rhodium (Rh) isharder than silver (Ag) and aluminum (Al), the scribing cutter does notbecome clogged as easily as with one of the softer metals. Accordingly,by forming the reflective layer from rhodium (Rh), the scribing processcan be improved.

[0067] Also, rhodium (Rh), ruthenium (Ru), platinum (Pt), gold (Au),nickel (Ni), cobalt (Co), and palladium (Pd), have comparatively goodcorrosion resistance and can be useful if the preferredcorrosion-resistant layer is not formed.

[0068] Further, because Rhodium (Rh), ruthenium (Ru), nickel (Ni), andcobalt (Co) also exhibit comparatively good adhesion to the substrate,they are useful if the preferred light transmission layer is not formedon the wafer. For example, as an alternative to the light transmissionlayer or a portion of the reflection layer, about 15 Å of a metal layercomprising rhodium (Rh) can be formed as the first layer of thelaminated reflective layer. By applying an alternative layer such asrhodium (Rh) which has a comparatively high reflectivity, thereflectivity of final mirror structure is not degraded and theresistance of mirror layer to delamination from the substrate can beimproved.

[0069] Because gold (Au) has a higher reflectivity than aluminum (Al) tored light, it is useful for forming the reflection layer in asemiconductor light-emitting device which emits light of comparativelylonger wavelength.

[0070] Because rhodium (Rh), ruthenium (Ru), platinum (Pt), gold (Au),and their alloys do not tend to react strongly with atmospheric gasesduring deposition or sputtering processes, those metals can also be usedto construct a mirror structure having high reflectivity without formingan underlying light transmission layer.

[0071] By forming layers in the mirror structure, such as the lighttransmission layer, and/or the reflective layer, and/or thecorrosion-resistant layer, in sequence by sputtering or depositing onlyafter forming the split lines, the split line formation process can beimproved.

[0072] After the light transmission layer is formed, the adhesivematerials from the adhesive sheet do not volatilize and form unwantedgases. That is because, as explained later in reference to FIG. 6, thesurface of the adhesive sheet where adhesive materials are exposed iscovered by the light transmission layer materials during the subsequentdeposition and sputtering processes. As a result, the adhesive materialsdo not volatilize additional gases and gases volatilized from theadhesive materials during the formation of the light transmission layerhave been exhausted, those gases are not present to combine chemicallywith the metals which are being deposited and sputtered to form thereflective layer. Accordingly, excellent reflectivity of the metal layer(the reflective layer) which is subsequently deposited on the lighttransmission layer can be maintained.

[0073] For the above described reasons, the process for forming splitlines (scribe lines) on the reverse side of the semiconductor wafer (thereverse side of the substrate) before forming the mirror structure (thereflective layer) is improved.

[0074] The thickness of the light transmission layer can be in a rangebetween 5 nm and 10 μm. Although it may depend on the kind ofmaterial(s) constituting the layer, the thickness of the lighttransmission layer is more preferably in a range between 15 nm and 500nm, and most preferably in a range between 20 nm and 300 nm. When thelight transmission layer is too thin, the surface of the adhesive sheetwhere adhesive materials are exposed is not sufficiently covered and gasgeneration cannot be prevented. As a result, metals being deposited onthe light transmission layer chemically combine with the gases releasedfrom beneath the light transmission layer. When this reaction occurs,the reflectivity of the mirror structure deteriorates and the adhesionbetween the mirror structure and the substrate decreases.

[0075] When the layer is too thick, its luminous transparency isdecreased and too much material, processing time and other resources arerequired to form the layer, thereby unnecessarily increasing the cost offorming the light transmission layer.

[0076] By carrying out the breaking process to divide the semiconductorwafer into individual light-emitting semiconductor devices, theproduction of merchandise such as light-emitting devices becomespossible. Alternatively, the breaking process can be omitted. Forexample, a purchaser of an undivided semiconductor wafer may choose tocarry out its own process to divide the wafers into separatelight-emitting semiconductor devices.

[0077] The substrate on which semiconductor crystals grow may comprisematerials such as sapphire, spinel, silicon, silicon carbide, zincoxide, gallium phosphide, gallium arsenide, magnesium oxide, manganeseoxide, lithium gallium oxide (LiGaO₂), and molybdenum sulfide (MoS).

[0078] Although it depends on other conditions such as the width of theseparation grooves, the kinds and thicknesses of materials formed on thesubstrate, and the thickness of the substrate after carrying out thelamellar process, the depth of the separation grooves formed on thesubstrate is, for example, about {fraction (1/30)} to about ½ of thethickness of a sapphire substrate. More preferably, the depth of theseparation grooves may be around 5-15% of the substrate thickness. Whenthe separation grooves are too deep, the semiconductor wafer will bemore prone to fail, e.g., form partial cracks during the formation ofthe separation grooves, the lamellar process, or the scribing process.These cracks in turn prevent the wafer from being divided cleanly intothe desired individual light-emitting devices and increase the number ofdefective units. When the depth of the separation grooves is tooshallow, the wafer may not be easily or cleanly divided during thebreaking process to produce the desired individual devices.

[0079] These effects can be seen in an LED comprising semiconductorlayers which comprise binary, ternary or quaternary semiconductorcompounds satisfying the formula Al_(x)Ga_(y)In_(1-x-y)N (0≦x≦1, 0≦y≦1,0≦x+y≦1), such as a light-emitting device using a group III nitridecompound semiconductor. Alternatively, a portion of the group IIIelements may be replaced with boron (B) or thallium (Tl), and a portionor all of nitrogen (N) may be replaced with phosphorous (P), arsenic(As), antimony (Sb), or bismuth (Bi).

[0080] First Embodiment

[0081]FIG. 1 is a cross-sectional view showing the structure of alight-emitting device 100 using group III nitride compound semiconductor(hereinafter referred to as a light-emitting semiconductor device 100 orsimply as a device 100). The light-emitting device 100 has almost thesame structure as that of a conventional light-emitting semiconductordevice 900 shown in FIG. 14, but the light-emitting device 100 furthercomprises a mirror structure 10 for reflecting light formed on thereverse side of a substrate 11.

[0082] The structure of the light-emitting semiconductor device 100 ofthe present invention is described more fully below.

[0083] The light-emitting semiconductor device 100 comprises a substrate11, preferably formed into an approximately square shape. On thesubstrate 11, a buffer layer 12 consisting of aluminum nitride (AlN),which has a thickness of about 25 nm, and an n⁺-layer (an n-type contactlayer) 13 having a high carrier concentration consisting of silicon (Si)doped GaN, which has a thickness of about 4.0 μm, are formed insequence. An additional layer of about 0.5 μm of Si-doped GaN is thenformed as an n-type clad layer 14 on the n⁺-layer (n-type contact layer)13.

[0084] An emission layer 15 having a multiple quantum well (MQW)structure is then formed on the n-type clad layer 14. The emission layer15 comprises 6 barrier layers 151, each of which has a thickness ofabout 35 Å and consists of GaN, and 5 well layers 152, each of which hasa thickness of about 35 Å and consists of Gao_(0.8)Ino_(0.2)N,alternately formed. About 50 nm of a p-type Al_(0.15)Gao_(0.85)N is thenformed on the emission layer 15 as a p-type clad layer 16. About 100 nmof a p-type GaN is then formed on the p-type clad layer 16 to act as ap-type contact layer 17.

[0085] A light-transmitting positive electrode 18A is then formed bydepositing metal on the p-type contact layer 17 and a negative electrode18B is formed on the n⁺-layer 13. The positive electrode 18A isconstructed from about 15 Å of cobalt (Co), which contacts the p-typecontact layer 17, and about 60 Å of gold (Au) , which is formed on thecobalt (Co). The negative electrode 18B is constructed from about 200 Åof vanadium (V) and about 1.8 μm of aluminum (Al) or an aluminum alloy.An electrode pad 20 having a thickness of about 1.5 μm is then formed onthe positive electrode 18A. The electrode pad 20 is preferably made fromcobalt (Co), nickel (Ni), gold (Au), aluminum (Al), or an alloyincluding at least one of these metals.

[0086] A mirror structure 10 is then formed on the reverse side of thesubstrate 11. Its structure and laminating process are explained in moredetail below with reference to FIGS. 8 and 11).

[0087] A method for manufacturing the light-emitting device 100according to the present invention includes the following steps.

[0088] Each of the layers of the light-emitting device 100 is formed bygaseous phase epitaxial growth, called metal organic vapor phasedeposition (hereinafter MOVPE). The gases employed in this process wereammonia (NH₃), a carrier gas (H₂ or N₂), trimethyl gallium (Ga(CH₃)₃)(hereinafter TMG), trimethyl aluminum (Al(CH₃)₃) (hereinafter TMA),trimethyl indium (In(CH₃)₃) (hereinafter TMI), silane (SiH₄), andbiscyclopentadienyl magnesium (Mg(C₅H₅)₂) (hereinafter CP₂Mg)

[0089] The single crystal sapphire substrate 11 was placed on asusceptor in a reaction chamber for the MOVPE treatment after its mainsurface ‘a’ has been cleaned by an organic washing solvent and heattreatment. Then the sapphire substrate 11 was baked at 1100° C. in H₂vapor fed into the chamber for 30 minutes under normal pressure.

[0090] About 25 nm of AlN buffer layer 12 was then formed on the surfaceof the baked sapphire substrate 11 under conditions controlled bylowering the temperature in the chamber to 400° C., keeping thetemperature constant, and concurrently supplying H₂, NH₃, and TMA.

[0091] About 4.0 μm of GaN was then formed on the buffer layer 12, as ann⁺-layer 13 having a high carrier concentration comprising an electronconcentration of at least about 2×10¹⁸/cm³, under conditions controlledby keeping the temperature of the sapphire substrate 11 at 1150° C. andconcurrently supplying H₂, NH₃, TMG, and silane.

[0092] About 0.5 μm of GaN was then formed on the n⁺-layer 13, to formclad layer 14, having a lower electron concentration of about1×10¹⁸/cm³, under conditions controlled by keeping the temperature ofthe sapphire substrate 11 at 1150° C. and concurrently supplying N₂ orH₂, NH₃, TMG, TMA, and silane.

[0093] Then about 35 Å A of a barrier layer 151 consisting of GaN wasformed under conditions controlled by concurrently supplying N₂ or H₂,NH₃, and TMG. And about 35 Å in thickness a well layer 152 consisting ofGa_(0.8)In_(0.2)N was then formed on the barrier layer 151 underconditions controlled by concurrently supplying N₂ or H₂, NH₃, TMG, andTMA. Similarly, four additional pairs comprising a barrier layer 151 anda well layer 152 were formed in sequence under the same respectiveconditions. A sixth barrier layer 151 consisting of GaN was then formedon the well layer 152 of the fifth pair. Accordingly, an emission layer15 having a multiple quantum well (MQW) structure with five periods wasformed.

[0094] About 50 nm of Mg-doped p-type Al_(0.15)Ga_(0.85)N was thenformed on the emission layer 15, to produce a clad layer 16, underconditions controlled by keeping the temperature of the substrate 11 at1100° C. and concurrently supplying N₂ or H₂, NH₃, TMG, TMA, and CP₂Mg.

[0095] About 100 nm of Mg-doped p-type GaN was then formed on the cladlayer 16, to form a contact layer 17, under conditions controlled bykeeping the temperature of the substrate at 1100° C. and concurrentlysupplying N₂ or H₂, NH₃, TMG, and CP₂Mg.

[0096] An etching mask was then formed on contact layer 17, andpredetermined regions of the mask were removed. Then the exposedportions of the contact layer 17, the clad layer 16, the emission layer15, the clad layer 14, and some part of the n⁺-layer 13 were etched byreactive ion etching using a gas including chlorine (Cl). Accordingly, aportion of the n⁺-layer 13 was exposed.

[0097] Then an electrode 18A and a light-transmitting electrode 18B wereformed on the n⁺-layer 13 and the contact layer 17, respectively, asfollows.

[0098] (1) A photoresist layer was formed on the n⁺-layer 13. A windowwas formed on a predetermined region of the exposed surface of then⁺-layer 13 by patterning using photolithography. After exhausting adeposition chamber to a high vacuum of at least 10⁻⁶ Torr, about 200 Åof vanadium (V) and about 1.8 μm of aluminum (Al) were deposited on thewindow and the remaining photoresist. The photoresist layer on then⁺-layer 13 was then removed. Accordingly, the electrode 18B was formedon the exposed surface of the n⁺-layer 13.

[0099] (2) A second photoresist layer was formed on the contact layer17. The photoresist layer over the electrode forming portion of contactlayer 17 was then removed by patterning using photolithography to form awindow.

[0100] (3) After exhausting a deposition chamber to a high vacuum lowerthan 10⁻⁶ Torr, about 15 Å of cobalt (Co) and about 60 Å of gold (Au)were formed in sequence on the photoresist layer and the exposed surfaceof the contact layer 17.

[0101] (4) The wafer was taken from the deposition reaction chamber andthe cobalt (Co) and gold (Au) laminated on the photoresist layer wereremoved using a lift-off process, leaving electrode 18A on the contactlayer 17.

[0102] (5) To form an electrode pad 20 to improve subsequent bonding, awindow was formed in another photoresist layer to expose a portion ofelectrode 18A. About 1.5 μm of at least one of cobalt (Co) or nickel(Ni), and at least one of gold (Au), aluminum (Al), or an alloyincluding at least Au or Al were deposited on the photoresist layer andin the window. Then, as in the formation of electrode 18A, the metalfilm formed on the photoresist layer was removed using a lift-offprocess to leave electrode pad 20.

[0103] (6) After the atmosphere of the chamber was exhausted by a vacuumpump, O₂ gas is supplied until the pressure reached about 3 Pa. Underconditions controlled by keeping the pressure constant and keeping thetemperature of the atmosphere about 550° C., the sample was heated forabout 3 minutes. Accordingly, the contact layer 17 and the clad layer 16were converted to lower resistance p-type layers, and the contact layer17, the electrode 18A, the n⁺-layer 13 and electrode 18B, respectively,are alloyed.

[0104] Using the process represented by steps (1) to (6), asemiconductor wafer 200 which does not have a mirror structure wasformed.

[0105] The processes of forming the mirror structure and separating thewafer into light-emitting semiconductor devices 100 are explained belowwith reference to FIGS. 2-8.

[0106]FIG. 2 is a cross-sectional view of the semiconductor wafer 200showing a process of forming separation grooves. As shown in FIG. 2, aseparation groove 21, which has a depth sufficient to reach into thesubstrate 11, was formed by dicing the semiconductor wafer 200 using ablade 40 (a process of forming a separation groove). The depth of theseparation groove 21 into the substrate 11 (the depth from the mainsurface of the substrate) may be in a range between 6 μm and 15 μm. Inthis embodiment, the depth is adjusted to be about 10 μm.

[0107] The reverse side 11 b of the substrate 11 formed in thesemiconductor wafer 200 was then polished using a polishing machineuntil the substrate 11 become a lamella its thickness has beensubstantially reduced. Accordingly, a wafer whose sectional and planviews are shown in FIGS. 3 and 4, respectively, can be obtained. Asshown in FIG. 4, because the portion of the substrate 11 on which theseparation groove 21 is formed is thinner than other portions of thesubstrate 11, the separation groove 21 can be recognized visually fromthe reverse side 11 b of the substrate 11. Here FIGS. 3 and 4 are aschematic cross-sectional view and a schematic plan view from thesubstrate side (from the reverse side 11 b).

[0108] An adhesive sheet 24 which is supported by support ring 60preferably made of stainless steel was then adhered on the electrodeside of the wafer. Accordingly, a wafer whose cross-sectional and planviews are shown in FIGS. 5 and 6A, respectively, can be obtained. HereFIG. 5 is a schematic cross-sectional view of the semiconductor wafer200 which comprises the adhesive sheet 24 after the adhering process(referred to as a semiconductor wafer 201) and FIGS. 6A and 6B areschematic plan views of the semiconductor wafer 201 from the substrateside which explains the adhering process and the scribing process.

[0109] As shown in FIG. 6B, split lines 25 were formed by scribing thereverse side 11 b of the substrate 11 opposite and along the separationgrooves 21. FIG. 7 is a cross-sectional view of the semiconductor wafer201 after forming the split lines 25 via the scribing process.

[0110] Then, by following the process described below, a mirrorstructure 10 was formed by sequentially laminating a light transmissionlayer 101, a reflective layer 102, and a corrosion-resistant layer 103on the reverse side 11 b of the substrate 11.

[0111] (Execution Condition for Sputtering)

[0112] (1) a light transmission layer 101 (about 30 nm of Al₂O₃)

[0113] (a) sputtering type: RF sputtering (100W)

[0114] (b) ultimate degree of vacuum in the atmosphere of a sputteringchamber: 2×10⁻⁴Pa

[0115] (c) gas pressure of inert gases used for pressure: 4×10⁻¹Pa (Argas)

[0116] (2) a reflective layer 102 (about 300 nm of Al)

[0117] (a) sputtering type: DC sputtering (200 mA, 380V)

[0118] (b) ultimate degree of vacuum in the atmosphere of a sputteringchamber: 2×10⁻⁴Pa

[0119] (c) gas pressure of inert gases used for pressure: 4×10⁻¹Pa (Argas)

[0120] (3) a corrosion-resistant layer 103 (about 100 nm in thickness ofAl₂O₃)

[0121] (a) sputtering type: RF sputtering (100W)

[0122] (b) ultimate degree of vacuum in the atmosphere of a sputteringchamber: 2×10⁻⁴Pa

[0123] (c) gas pressure of inert gases used for pressure: 4×10⁻¹Pa (Argas)

[0124] Accordingly, the mirror structure 10 shown in FIG. 8 can beobtained. FIG. 8 is a schematic cross-sectional view of thesemiconductor wafer 201 after forming the mirror structure.

[0125] The wafer was then divided into individual chips by mechanicallyloading the wafer near the split line to break the wafer and separatethe light-emitting devices shown in FIG. 1.

[0126] By forming the mirror structure 10 on the reverse side of thesubstrate 11, deterioration of the reflectivity of the reflective layer102 can be prevented. As a result, light emitted downwardly fromemission layer 15 can be reflected effectively to provide a highluminous intensity. For example, luminous intensity of thelight-emitting device 100 manufactured by applying the method describedabove is about 130% of that achieved by a conventional light-emittingsemiconductor device which does not have a mirror structure formed onthe reverse side of its substrate.

[0127]FIG. 9 is a table showing characteristics of a light-emittingdevice 100 using a group III nitride compound semiconductor devicecorresponding to wafer 201 as shown in FIG. 8 after applying electricitycontinuously for a given period. Here luminous intensity maintenancerate (%) represents a ratio (percentage) of the luminous intensity ofthe light-emitting semiconductor device 100 after applying electricitycontinuously to the initial luminous intensity of the device 100. Asshown in the table of FIG. 9, after applying electricity continuouslyfor 500 hours, the luminous intensity of the light-emitting device 100according to the present invention which comprises the mirror structure10 is larger than that of the light-emitting device 900 which comprisesa conventional mirror structure 90.

[0128] Unlike the above embodiment, the light transmission layer 101,the reflection layer 102, and the corrosion-resistant layer 103 can beformed after separation of the light-emitting devices if so desired.

[0129] Second Embodiment

[0130] In this embodiment, a method for manufacturing a light-emittingdevice 100 using a group III nitride compound semiconductor, which isshown in FIG. 1, from a semiconductor wafer 300 shown in FIG. 4 isexplained.

[0131]FIG. 4 is a plan view of the semiconductor wafer 300 viewed fromthe substrate side (11 b) after carrying out the polishing process. Thesemiconductor wafer 300 is the same as the semiconductor wafer 200 inthe first embodiment.

[0132] The semiconductor wafer 300 was cleaned using an organic washingsolvent such as acetone, IPA, etc. with the temperature of the surfaceof the substrate being raised to about 150° C.

[0133] FIGS. 10A-10C are views showing a process for forming a mask.FIGS. 10A and 10B are plan views and FIG. 10C is a cross-sectional viewof the semiconductor wafer 300 showing processes of forming a mask andthe mirror structure.

[0134] As shown in FIG. 10A, the light-emitting device 100 using a groupIII nitride compound semiconductor, which is to be separated from thesemiconductor wafer 300, is formed in an approximate square each ofwhose edges (L1) is about 330 μm.

[0135] An attached mask 70 made of stainless steel formed in a reticulargrid pattern shown in FIG. 10B. A width D2 of the striped parts of thisgrid pattern which are masked by the attached mask 70 is three times aslarge as a width L2 of the striped parts of the separation groove 21.

[0136] As shown in FIG. 10C, the attached mask 70 is positionedapproximately parallel to the reverse side 11 b of the substrate 11.Also, the center lines of the width D2 of the striped parts of theattached mask 70 approximately correspond to that of the width L2 of theseparation grooves 21. Accordingly, the process of forming the mask iscarried out.

[0137] A distance between the reverse side 11 b of the substrate 11 andthe attached mask 70 may be determined according to the thickness,materials, etc. of the mirror structure 10 to be formed thereon.Alternatively, the distance between the reverse side 11 b and theattached mask 70 can be about 0 μm (in contact). Alternatively, thetemperature of the surface of the substrate 11 can be raised bysupplying electric current to the attached mask 70 to heat it. Thetemperature of the surface of the substrate 11 need not, however beraised.

[0138]FIG. 11 is a schematic cross-sectional view of the semiconductorwafer 300 after the process of forming the mirror structure whichincludes the masking process explained above. The reflective layer 1020preferably has a multiple layer structure comprising about 900 Å of Aglayer 102 a, about 300 Å of Ni/Mo layer 102 b, and about 3000 Å of Aulayer 102 c. These metal layers are preferably formed by carrying outsequential electron beam depositions.

[0139] A corrosion-resistant layer 103 was formed under almost the sameconditions as that explained in the first embodiment. Thecorrosion-resisting layer 103 of this embodiment is, however, optional.

[0140] For a mirror structure 10 having the structure described in thisembodiment, the reflectivity of a reflective layer saturates when thethickness of the reflective layer is in a range of about 800 Å to 1000Å. As a result, sufficiently high reflectivity and excellent corrosionresistance can be obtained at the same time. That is, the mirrorstructure 10 of the second embodiment can obtain almost the same degreeof high reflectivity and excellent corrosion resistance as the mirrorstructure 10 of the first embodiment.

[0141] After carrying out the same adhesion process as in the firstembodiment, a semiconductor wafer 301 comprising an adhesive sheet 24whose cross-sectional view is shown in FIG. 12 was obtained.

[0142] Then the same scribing process as described in the firstembodiment is carried out, and a semiconductor wafer 301 comprising asplit lines 25 whose cross-sectional view is shown in FIG. 13 wasobtained.

[0143] Then, the wafer was divided into chips by mechanically loadingthe wafer near the split lines to break the wafer and separate thelight-emitting devices shown in FIG. 1.

[0144] Accordingly, by forming the mirror structure 10 on the reverseside of the substrate 11, the reflectivity of the reflective layer 1020(especially the layer 102 a which is the main layer for reflecting theemitted light) can be prevented from deteriorating. As a result, lightemitted from the emission layer 15 can be reflected effectively tomaintain high luminous intensity over extended periods.

[0145] Because the mirror structure 10 is not formed on the portionswhere the split lines will be later formed, the separation groove 21 canbe recognized visually from the mirror structure side (reverse side) ofthe semiconductor wafer during the scribing process. Thus scribing afterforming the mirror structure on the reverse side of the substrate 11becomes easy. Also, dividing the semiconductor wafer 301 into pieces ofdevice 100 becomes easy because of the split line.

[0146] In the second embodiment, an adhesive sheet is not used in theprocess of forming the mirror structure. Because of this, washing andheating the semiconductor wafer 300 at this stage becomes possible. Andbecause an adhesive sheet is not adhered, unwanted gases cannot bevolatilized during mirror formation. That enables the formation of amirror structure having high reflectivity and adhesiveness without theneed to form an underlying light transmission layer on the substrate.

[0147] A metal layer of about 1000 Å consisting of rhodium (Rh) can beformed in place of the multiple layer structure of reflective layer1020. Rh exhibits excellent adhesion to the substrate and also providescomparatively good corrosion resistance and reflectivity. Thus, byforming a metal layer consisting of such metals, excellent adhesion andreflectivity can be obtained.

[0148] The attached mask consists of stainless steel having a thicknessin a range of 20 μm to 500 μm. The thickness of the attached mask ismore preferably in a range of about 30 μm to 300 μm, somewhat morepreferably in a range of about 30 μm to 100 μm and most preferablyaround 50 μm. When the attached mask is too thin, the mask may be easilydamaged thereby preventing its reuse. When the attached mask is toothick, the thickness of the mirror structure around a boundary of theedge of a region on which the mask is formed tends to become irregularand an accurately attached mask cannot be obtained.

[0149] The width of the striped parts of the grid pattern which aremasked by the attached mask is preferably in a range about one to tentimes that of the width of the striped parts of the separation groove.Although it may depend on the width of the separation groove, the widthof the striped parts of the attached mask is preferably in a range ofabout two to five times larger than the width of the separation groove,and more preferably about three times larger than that of the separationgroove. When the width of the striped parts masked by the attached maskis too large, the effective area of the mirror structure becomesnarrower and the quantity of reflected lights decreases. When the widthof the striped parts masked by the attached mask is too small,considerable accuracy is required for positioning the mask and, afterthe mirror structure is formed, the separation groove may be difficultto recognize from the reverse side thereby increasing the difficulty inpositioning a scribing cutter precisely.

[0150] In the above embodiments, the emission layer 15 formed in thelight-emitting device 100 has a multiple quantum well (MQW) structure.Alternatively, the emission layer 15 can have a single quantum well(SQW) structure, a single layer structure which comprises a layerconsisting of materials such as Ga_(0.8)In_(0.2)N, quaternary or ternaryAlGaIn having an arbitrary composition ratio, etc. In the embodiments,magnesium (Mg) is used as a p-type impurity. Alternatively, group IIelements such as beryllium (Be) and zinc (Zn) can be used as a p-typeimpurity.

[0151] The present invention can be applied to a light-emitting devicesuch as an LED and an LD. Also the present invention can also be appliedto a light-receiving device.

[0152] While the invention has been described in connection with whatare presently considered to be the most practical and preferredembodiments, it is to be understood that the invention is not to belimited to the disclosed embodiments but, on the contrary, is intendedto cover various modifications and equivalent arrangements includedwithin the spirit and scope of the appended claims.

What is claimed is:
 1. A light-emitting semiconductor device comprising:a substrate; plural semiconductor layers comprising group III nitridecompound semiconductors laminated on the substrate; an emission layerformed on a first side of the substrate; and a mirror structure formedon a second side of the substrate opposite the first side, wherein themirror structure comprises a light transmission layer having luminoustransparency comprising at least one material selected from a groupconsisting of metal oxides and ceramics, and a metal reflective layersuitable for reflecting light emitted from the emission layer.
 2. Alight-emitting semiconductor device comprising: a substrate; pluralsemiconductor layers comprising group III nitride compoundsemiconductors laminated on the substrate; an emission layer; and amirror structure, wherein the mirror structure comprises a metalreflective layer suitable for reflecting light emitted from the emissionlayer and a corrosion-resistant layer comprising at least one materialselected from the group consisting of metal oxides and ceramics.
 3. Alight-emitting device comprising a group III nitride compoundsemiconductor according to claim 1, further comprising acorrosion-resistant layer which comprises at least one metal oxide orceramic material formed on an exposed surface of the mirror structure.4. A light-emitting device using a group III nitride compoundsemiconductor according to claim 1, wherein the reflective layer isformed by using at least one metal from a group consisting of aluminum(Al), silver (Ag), and their alloys.
 5. A light-emitting device using agroup III nitride compound semiconductor according to claim 2, whereinthe reflective layer is formed by using at least one metal from a groupconsisting of aluminum (Al), silver (Ag), and their alloys.
 6. Alight-emitting device using a group III nitride compound semiconductoraccording to claim 1, wherein the thickness of the reflective layer isin a range of 5 nm to 20 μm.
 7. A light-emitting device using a groupIII nitride compound semiconductor according to claim 2, wherein thethickness of said reflective layer is in a range of 5 nm to 20 μm.
 8. Alight-emitting device using a group III nitride compound semiconductoraccording to claim 1, wherein said light transmission layer comprises atleast one material selected from a group of metal oxides and oxidesconsisting of Al₂O₃, TiO₂, MgO, MgCO₃, Ta₂O₅, ZnO, In₂O₃, SiO₂, SnO₂,and ZrO₂.
 9. A light-emitting device using a group III nitride compoundsemiconductor according to claim 2, wherein said light transmissionlayer comprises at least one material selected from a group of metaloxides and oxides consisting of Al₂O₃, TiO₂, MgO, MgCO₃, Ta₂O₅, ZnO,In₂O₃, SiO₂, SnO₂, and ZrO₂.
 10. A light-emitting device using a groupIII nitride compound semiconductor according to claim 4, wherein saidlight transmission layer comprises at least one material selected from agroup of metal oxides and oxides consisting of Al₂O₃, TiO₂, MgO, MgCO₃,Ta₂O₅, ZnO, In₂O₃, SiO₂, SnO₂, and ZrO₂.
 11. A light-emitting deviceusing group III nitride group compound semiconductor according to claim5, wherein said light transmission layer comprises at least one materialselected from a group of metal oxides and oxides consisting of Al₂O₃,TiO₂, MgO, MgCO₃, Ta₂O₅, ZnO, In₂O₃, SiO₂, SnO₂, and ZrO₂.
 12. Alight-emitting device using group III nitride group compoundsemiconductor according to claim 6, wherein said light transmissionlayer comprises at least one material selected from a group of metaloxides and oxides consisting of Al₂O₃, TiO₂, MgO, MgCO₃, Ta₂O₅, ZnO,In₂O₃, SiO₂, SnO₂, and ZrO₂.
 13. A light-emitting device using group IIInitride group compound semiconductor according to claim 7, wherein saidlight transmission layer comprises at least one material selected from agroup of metal oxides and oxides consisting of Al₂O₃, TiO₂, MgO, MgCO₃,Ta₂O₅, ZnO, In₂O₃, SiO₂, SnO₂, and ZrO₂.
 14. A light-emitting deviceusing a group III nitride compound semiconductor according to claim 1,wherein a thickness of the light transmission layer is in a range ofabout 5 nm to 10 μm.
 15. A light-emitting device using a group IIInitride compound semiconductor according to claim 8, wherein a thicknessof the light transmission layer is in a range of about 5 nm to 10 μm.16. A light-emitting device using a group III nitride compoundsemiconductor according to claim 9, wherein a thickness of said lighttransmission layer is in a range of 5 nm to 10 μm.
 17. A light-emittingdevice using a group III nitride compound semiconductor according toclaim 10, wherein a thickness of the light transmission layer is in arange of about 5 nm to 10 μm.
 18. A light-emitting device using a groupIII nitride compound semiconductor according to claim 11, wherein athickness of the light transmission layer is in a range of about 5 nm to10 μm.
 19. A light-emitting device using a group III nitride compoundsemiconductor according to claim 12, wherein a thickness of the lighttransmission layer is in a range of about 5 nm to 10 μm.
 20. Alight-emitting device using a group III nitride compound semiconductoraccording to claim 13, wherein a thickness of the light transmissionlayer is in a range of about 5 nm to 10 μm.
 21. A light-emitting deviceusing group III nitride group compound semiconductor according to claim2, wherein the corrosion-resistant layer comprises at least one materialselected from a group consisting of Al₂O₃, TiO₂, MgO, MgCO₃, Ta₂O₅, ZnO,In₂O₃, SiO₂, ZrO₂, metal carbides, metal nitrides, and metal borides.22. A light-emitting device using a group III nitride compoundsemiconductor according to claim 2, wherein a thickness of thecorrosion-resisting layer is in a range of about 5 nm to 10 μm.
 23. Alight-emitting device using a group III nitride compound semiconductoraccording to claim 21, wherein a thickness of the corrosion-resistinglayer is in a range of about 5 nm to 10 μm.
 24. A light-emitting deviceusing a group III nitride compound semiconductor according to claim 1,wherein the substrate comprises sapphire and has a thickness in a rangeof about 75 μm to 150 μm.
 25. A light-emitting device using a group IIInitride compound semiconductor according to claim 2, wherein thesubstrate comprises sapphire and has a thickness in a range of about 75μm to 150 μm.
 26. A light-emitting device using a group III nitridecompound semiconductor according to claim 1, wherein the reflectivelayer is comprises at least one metal selected from a group consistingof rhodium (Rh), ruthenium (Ru), platinum (Pt), gold (Au), copper (Cu),palladium (Pd), chromium (Cr), nickel (Ni), cobalt (Co), titanium (Ti),indium (In), molybdenum (Mo), and their alloys.
 27. A light-emittingdevice using a group III nitride group compound semiconductor accordingto claim 2, wherein the reflective layer comprises at least one metalselected from a group consisting of rhodium (Rh), ruthenium (Ru),platinum (Pt), gold (Au), copper (Cu), palladium (Pd), chromium (Cr),nickel (Ni), cobalt (Co), titanium (Ti), indium (In), molybdenum (Mo),and their alloys.
 28. A light-emitting device using a group III nitridegroup compound semiconductor according to claim 8, wherein thereflective layer comprises at least one metal selected from a groupconsisting of rhodium (Rh), ruthenium (Ru), platinum (Pt), gold (Au),copper (Cu), palladium (Pd), chromium (Cr), nickel (Ni), cobalt (Co),titanium (Ti), indium (In), molybdenum (Mo), and their alloys.
 29. Alight-emitting device using a group III nitride group compoundsemiconductor according to claim 9, wherein the reflective layercomprises at least one metal selected from a group consisting of rhodium(Rh), ruthenium (Ru), platinum (Pt), gold (Au), copper (Cu), palladium(Pd), chromium (Cr), nickel (Ni), cobalt (Co), titanium (Ti), indium(In), molybdenum (Mo), and their alloys.
 30. A light-emitting deviceusing a group III nitride compound semiconductor according to claim 1,wherein the reflective layer has a multi-layer structure comprising aplurality of metal layers.
 31. A light-emitting device using a group IIInitride compound semiconductor according to claim 2, wherein thereflective layer has a multi-layer structure comprising a plurality ofmetal layers.
 32. A method for manufacturing a light-emitting deviceusing a group III nitride compound semiconductor according to claim 1,comprising a process of: forming a mirror structure, wherein saidprocess comprises the steps of sequentially forming a light transmissionlayer, a reflective layer, and a corrosion-resistant layer.
 33. A methodfor manufacturing a light-emitting device using a group III nitridecompound semiconductor according to claim 2, comprising a process of:forming a mirror structure, wherein said process comprises the steps ofsequentially forming a light transmission layer, a reflective layer, anda corrosion-resistant layer.
 34. A method for manufacturing alight-emitting device using a group III nitride compound semiconductoraccording to claim 32, further comprising a step of: a breaking processfor separating the semiconductor wafer into individual light-emittingdevices.
 35. A method for manufacturing a light-emitting device using agroup III nitride compound semiconductor according to claim 33, furthercomprising a step of: a breaking process for separating thesemiconductor wafer into individual light-emitting devices.
 36. A methodfor manufacturing a light-emitting device using a group III nitridecompound semiconductor according to claim 32, further comprising thesteps of: a process for forming separation grooves for separating thesemiconductor wafer into individual light-emitting semiconductor devicesby cutting the electrode side of, said wafer to a predetermined depth; alamellar process comprising grinding or polishing the substrate to apredetermined thickness; an adhesion process for adhering thesemiconductor wafer to an adhesive sheet to expose a surface of thesubstrate; a scribing process for scribing split lines into the exposedsurface of the substrate for dividing the wafer into individuallight-emitting semiconductor devices; and a process for forming themirror structure on the exposed surface of the substrate.
 37. A methodfor manufacturing a light-emitting device using a group III nitridecompound semiconductor according to claim 33, further comprising thesteps of: a process for forming separation grooves for separating thesemiconductor wafer into individual light-emitting semiconductor devicesby cutting an electrode side of the wafer to a predetermined depth; alamellar process comprising grinding or polishing the substrate to apredetermined thickness; an adhesion process for adhering thesemiconductor wafer to an adhesive sheet to expose a surface of thesubstrate; a scribing process for scribing split lines on the exposedsurface of the substrate dividing the wafer into individuallight-emitting semiconductor devices; and a process for forming themirror structure.